Cold induces increased ad libitum energy intake independent of changes in energy expenditure: a controlled crossover trial in adults.

Background: Measures of energy metabolism [energy expenditure (EE), respiratory exchange ratio (RER)] have been associated with ad libitum energy intake (EI) and weight gain in previous observational studies, suggesting that energy-sensing mechanisms drive EI to meet metabolic energy demands.

Objective: We aimed to employ mild cold exposure as an intervention to alter energy metabolism and evaluate its causal effects on concurrent and next day ad libitum EI.

Methods: In a controlled crossover study, 47 volunteers (16 female; age 37.2±10.7 years; BMI 32.4±8.6 kg/m) completed four 24-h EE measurements in a respiratory chamber. Participants ate ad libitum for 24-h using an objective vending machine paradigm while in the chamber during both cold exposure (19°C) and thermoneutral conditions (23.5°C) and after two eucaloric chamber stays with exposure to each temperature. Energy metabolism changes were calculated from eucaloric conditions (cold vs. thermoneutral).

Results: Compared to thermoneutral conditions, participants consumed 13% more while residing in the chamber during cold (mean difference: 411±987 kcal/day, p=0.006), but not the day after cold exposure. Neither eucaloric EE, RER, nor carbohydrate oxidation (CARBOX) were significantly changed by cold exposure. However, greater increases in RER and CARBOX during cold exposure were associated with greater ad libitum EI on the day after cold exposure (r=0.29, p=0.049 and r=0.33, p=0.02), but not with EI during cold exposure. Cold-induced changes in 24-h EE were not associated with changes in ad libitum EI during or after cold exposure.

Conclusion: Ad libitum EI increased during but not following mild cold exposure. There was an effect of 24-h RER and CARBOX during cold exposure that was related to greater ad libitum EI following cold. These results indicate an acute effect of cold on concurrent EI independent of changes in metabolic rate, but also a residual influence of cold on subsequent EI via fuel preference. CLINICAL TRIAL REGISTRATION NUMBER (FROM CLINICALTRIALS.GOV): NCT02939404.